Reduced-noise ducted flow hair dryer with multiple impellers and ambient air inlets

Abstract

An axial flow hair dryer comprises a generally circular main housing with a transitional portion that smoothly reduces the housing diameter to an outlet. A first fan stage in the main housing generates an axial air flow through the housing. An outer duct has two axial extensions secured to the housing near the beginning of the transitional portion, and the housing air outlet introduces air exiting the housing into the outer duct. The housing and the outer duct form two additional ambient air intakes extending between the axial extensions in a smooth arc toward the main housing outlet. A second fan stage includes a second axial flow impeller in the outer duct for generating air flow through the ambient air intake. The second axial flow impeller includes inner and outer blades separated by an annular shroud that forms an extension of the main housing flow passage. A guide duct in the outer duct forms a further extension of the extended air flow passage, and the guide duct includes stator vanes at its outlet. A handle depending from the main housing holds a motor and a flex shaft connects the motor to a drive shaft that carries both fan stages. Resistance heating wires in the main housing heat the air flowing through the hair dryer.

What is claimed is: 
     
       1. An axial flow hair dryer comprising: a housing forming an air flow passage between an air inlet for ambient air and an air outlet;   a first axial flow impeller disposed in said housing for generating an ambient air flow into said air flow passage through said housing air inlet;   an outer duct having an air inlet and an air outlet, said outer duct being secured to said housing with said housing air outlet disposed to introduce air flow exiting said housing air outlet into said outer duct and to form between said housing and said outer duct an air intake for ambient air;   a second axial flow impeller disposed in said outer duct for generating an ambient air flow into said outer duct through said air intake;   driving means for supplying motive force to said first axial flow impeller and second axial flow impeller; and   heating means for heating air flowing through said hair dryer and exiting said outer duct air outlet.   
     
     
       2. An axial flow hair dryer as in claim 1, wherein said first axial flow impeller and said second axial flow impeller are mounted on a single drive shaft. 
     
     
       3. An axial flow hair dryer as in claim 2, wherein: said housing comprises a handle depending from said housing; and   said driving means comprises a motor disposed in said handle and connected to said drive shaft by a flexible drive shaft.   
     
     
       4. An axial flow hair dryer as in claim 3, wherein said second axial flow impeller includes a plurality of inner blades and a plurality of outer blades separated by an annular shroud that forms an extension of said air flow passage formed by said housing. 
     
     
       5. An axial flow hair dryer as in claim 4, further comprising a stator stage disposed in said outer duct downstream of said second axial flow impeller, said stator stage including a plurality of inner vanes and a plurality of outer vanes separated by an annular shroud that forms an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller. 
     
     
       6. An axial flow hair dryer as in claim 1, further comprising at least one stator stage disposed in said outer duct downstream of said second axial flow impeller. 
     
     
       7. An axial flow hair dryer comprising: a housing forming an air flow passage between an air inlet for ambient air and an air outlet;   a first axial flow impeller disposed in said housing for generating an ambient air flow into said air flow passage through said housing air inlet;   an outer duct having an air inlet and an air outlet, said outer duct being secured to said housing with said housing air outlet disposed to introduce air flow exiting said housing air outlet into said outer duct and to form between said housing and said outer duct an air intake for ambient air;   a second axial flow impeller disposed in said outer duct for generating an ambient air flow into said outer duct through said air intake, said second axial flow impeller including a plurality of inner blades and a plurality of outer blades separated by an annular shroud that forms an extension of said air flow passage formed by said housing;   a guide duct disposed in said outer duct forming an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller, wherein said guide duct has an outlet at substantially the same axial location as said outlet of said outer duct and includes a plurality of generally radial stator vanes;   driving means for supplying motive force to said first axial flow impeller and second axial flow impeller; and   heating means for heating air flowing through said hair dryer and exiting said outer duct air outlet.   
     
     
       8. An axial flow hair dryer as in claim 7, wherein said stator vanes extend from a central hub to said outer duct. 
     
     
       9. An axial flow hair dryer as in claim 8, further comprising a stator stage disposed in said outer duct downstream of said second axial flow impeller, said stator stage including a plurality of inner vanes and a plurality of outer vanes separated by an annular shroud that forms an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller. 
     
     
       10. An axial flow hair dryer as in claim 7, wherein said outer duct outlet generally lies in a plane at an oblique angle to an axis of said air flow exiting said outer duct outlet. 
     
     
       11. An axial flow hair dryer comprising: a housing forming an air flow passage between an air inlet for ambient air and an air outlet;   a first axial flow impeller disposed in said housing for generating an ambient air flow into said air flow passage through said housing air inlet;   an outer duct having an air inlet and an air outlet, said housing air outlet being disposed to introduce air flow exiting said housing air outlet into said outer duct and to form between said housing and said outer duct an air intake for ambient air, wherein said outer duct includes a plurality of axial extensions secured to said housing upstream of said housing air outlet;   a second axial flow impeller disposed in said outer duct for generating an ambient air flow into said outer duct through said air intake said second axial flow impeller including a plurality of inner blades and a plurality of outer blades separated by an annular shroud that forms an extension of said air flow passage formed by said housing;   driving means for supplying motive force to said first axial flow impeller and second axial flow impeller; and   heating means for heating air flowing through said hair dryer and exiting said outer duct air outlet.   
     
     
       12. An axial flow hair dryer as in claim 11, wherein: said housing is generally circular in cross section, said housing air inlet having a larger diameter than said housing air outlet and said housing including a transitional portion smoothly reducing the diameter of said air passage to said housing air outlet;   said axial extensions are secured to said housing proximate to an end of said transitional portion; and   said air intake includes a like plurality of intake portions, each being disposed between said axial extensions and extending toward said housing air outlet.   
     
     
       13. An axial flow hair dryer as in claim 12, wherein said plurality is two in number and said axial extensions are diametrically opposed to each other at the top and bottom of the outer duct, and said outer duct air intakes are diametrically opposed to each other and each extends in a smooth arc from said axial extensions toward said housing air outlet. 
     
     
       14. An axial flow hair dryer as in claim 12, further comprising a guide duct disposed in said outer duct forming an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller, wherein said guide duct has an outlet at substantially the same axial location as said outlet of said outer duct and includes a plurality of generally radial stator vanes at said outlet thereof. 
     
     
       15. An axial flow hair dryer as in claim 14, further comprising a stator stage disposed in said outer duct downstream of said second axial flow impeller, said stator stage including a plurality of inner vanes and a plurality of outer vanes separated by an annular shroud that forms an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller. 
     
     
       16. An axial flow hair dryer as in claim 14, wherein said outer duct outlet generally lies in a plane at an oblique angle to an axis of said air flow exiting said outer duct outlet. 
     
     
       17. An axial flow hair dryer comprising: a housing forming an air flow passage between an air inlet for ambient air and an air outlet, said housing being generally circular in cross section with said air inlet having a larger diameter than said air outlet and said housing including a transitional portion smoothly reducing the diameter of said air passage to said housing air outlet, wherein said housing includes a handle depending therefrom;   an integrally molded first fan stage including a first axial flow impeller disposed in said housing for generating an ambient air flow into said air passage through said housing air inlet;   an outer duct having an air inlet and an air outlet, said housing air outlet being disposed to introduce air flow exiting said housing air outlet into said outer duct and to form between said housing and said outer duct an air intake for ambient air, wherein said outer duct includes two axial extensions secured to said housing proximate to an end of said transitional portion, one said extension being disposed at substantially the same circumferential location as said handle and the other said extension being diametrically opposed thereto, said outer duct air intake includes two intake portions disposed between said axial extensions and extending in a smooth arc from said axial extensions toward said housing air outlet, and said outer duct outlet generally lies in a plane at an oblique angle to an axis of said air flow exiting said outer duct outlet;   an integrally molded second fan stage including a second axial flow impeller for generating an ambient air flow into said outer duct through said air intake, said second axial flow impeller being disposed in said outer duct and including a plurality of inner blades and a plurality of outer blades separated by an annular shroud that forms an extension of said air flow passage formed by said housing;   a guide duct disposed in said outer duct forming an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller, wherein said guide duct has an outlet at substantially the same axial location as said outlet of said outer duct and includes a plurality of generally radial stator vanes at said outlet thereof;   a motor mounted inside said handle;   support structure in said housing mounting a drive shaft for rotation, said first fan stage and said second fan stage being mounted to said drive shaft for rotation therewith;   a flex shaft for supplying motive force from said motor to said drive shaft; and   resistance heating means for heating air flowing through said hair dryer and exiting said outer duct air outlet.   
     
     
       18. An axial flow hair dryer as in claim 17, wherein said stator vanes extend from a central hub to said outer duct. 
     
     
       19. An axial flow hair dryer as in claim 18, further comprising a stator stage disposed in said outer duct downstream of said second axial flow impeller, said stator stage including a plurality of inner vanes and a plurality of outer vanes separated by an annular shroud that forms an extension of said extended air flow passage formed by said annular shroud of said second axial flow impeller. 
     
     
       20. A blower device comprising: a housing forming an air flow passage between an air inlet for ambient air and an air outlet;   a first axial flow impeller disposed in said housing for generating an ambient air flow into said air flow passage through said housing air inlet;   an outer duct having an air inlet and an air outlet, said outer duct being secured to said housing with said housing air outlet disposed to introduce air flow exiting said housing air outlet into said outer duct and to form between said housing and said outer duct an air intake for ambient air;   a second axial flow impeller disposed in said outer duct for generating an ambient air flow into said outer duct through said air intake; and   driving means for supplying motive force to said first axial flow impeller and second axial flow impeller.